1. Field of the Invention
The present invention relates to magnetic tape recording apparatuses and methods, magnetic tape reading apparatuses and methods, recording media used therewith, and magnetic tape formats. In particular, the present invention relates to a magnetic tape recording apparatus and method for recording high definition (HD) video data on a magnetic tape, a magnetic tape reading apparatus and method for reading HD video data from a magnetic tape, a magnetic tape format for use in the magnetic tape recording apparatus and method and the magnetic tape reading apparatus and method, and a recording medium used therewith.
2. Description of the Related Art
Along with an advanced compression technique, video data can be compressed and recorded on a magnetic tape according to a digital video (DV) system. A format therefor is defined as a DV format for consumer digital videocassette recorders.
FIG. 1 shows the configuration of one track of the DV format, which relates to the present invention. In the DV format, video data is recorded after being converted by twenty-four-to-twenty-five (24–25) conversion. The numbers of bits, shown in FIG. 1, indicate values obtained after the 24–25 conversion is performed.
An area of a magnetic tape which corresponds to a winding angle of 174 degrees is used as one substantial track portion. Outside the one track portion, an overwrite margin having a length of 1250 bits is formed. The overwrite margin prevents data from remaining after erasure.
When a rotary head is rotated while synchronizing with a frequency of 60×1000/1001, the one track portion has a length of 134975 bits. When the rotary head is rotated while synchronizing with a frequency of 60 Hz, the one track portion has a length of 134850 bits.
In the one track portion, an insert and track information (ITI) sector, an audio sector, a video sector, and a subcode sector are sequentially arranged in the trace direction (the left-to-right direction in FIG. 1) of the rotary head. A gap G1 is formed between the ITI sector and the audio sector, a gap G2 is formed between the audio sector and the video sector, and a gap G3 is formed between the video sector and the subcode sector.
The ITI sector has a length of 3600 bits, and includes a 1400-bit preamble, and a start sync area (SSA) and a track information area (TIA) which have a length of 1920 bits. In the SSA, a bit string (sync number) necessary for detecting the position of the TIA is provided. In the TIA, information representing the consumer DV format, information representing an SP mode or an LP mode, information representing the pattern of a pilot signal in one frame, etc., are recorded. The TIA is followed by a 280-bit postamble.
The gap G1 has a length of 625 bits.
The audio sector has a length of 11550 bits. Its first 400 bits are used as a preamble, and its last 500 bits are used as a postamble. The intermediate 10650 bits are used as data (audio data).
The gap G2 has a length of 700 bits.
The video sector has a length of 113225 bits. Its first 400 bits are used as a preamble, and its last 925 bits are used as a postamble. The intermediate 111900 bits are used as data (video data).
The gap G3 has a length of 1550 bits.
The subcode sector has a length of 3725 bits when the rotary head is rotated at a frequency of 60×1000/1001 Hz, and has a length-of 3600 bits when the rotary head is rotated at a frequency of 60 Hz. Its first 1200 bits are used as a preamble. In the former case, the last 1325 bits are used as a postamble, and in the latter case, the last 1200 bits are used as a postamble. The intermediate 1200 bits are used as data (subcode).
As described above, in the DV format, a so-called “overhead” is long because the ITI sector, the audio sector, the video sector, and the subcode sector not only have the gaps G1 to G3 thereamong, but also each have a preamble and a postamble, so that a sufficient data-recording rate cannot be obtained.
As a result, in the DV format, a video rate of, at most, approximately 24 Mbps can be ensured which corresponds to MP@HL in the MPEG system although a bit rate of approximately 25 Mbps is required for recording, for example, HD video data. Accordingly, in the DV format, standard definition (SD) video data can be recorded, but HD video data cannot be compressed by MP@HL, MP@H-14, etc., for recording.